Why are late answers from new users reviewed?
This simple question might appear somewhere in the meta FAQ or questions, but after searching for several minutes I can't find the logic clearly explained.
Anyone, not just new users, that answers an old question should be contributing to the existing body of knowledge already present with the other existing answers. Throwing it into the review queue is [in theory] a good way to check that. It also helps tease out gems and weed out poor answers.
The "Late Answers" review page is described with the following phrase:
For what I could notice on Drupal Answers, most of the late answers given from new users are related questions written as answers; requests for more information necessary to answer the question; comments about having the same problem, and asking to the OP if a solution was found; spam.
While not all the late answers are like this, between the late answers written by new users you can find answers that should be flagged as "not an answer." There are then answers that are only spam, which generally are written for old questions, even if I have also seen spammer using a question for spamming, and adding more spam as answers.
If then the answer is a perfectly valid answer, you could up-vote it.